i40iw: Remove unnecessary parameter to i40iw_cq_poll_completion

Post_cq parameter passed to i40iw_cq_poll_completion is always
true; so remove.

Signed-off-by: Mustafa Ismail <mustafa.ismail@intel.com>
Signed-off-by: Shiraz Saleem <shiraz.saleem@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>